Reciprocatory telescoping-piston hydraulic motor



June 9, 1964 R. E. WALKER 3,

RECIPROCATORY TELESCOPING-PISTON HYDRAULIC MOTOR Filed 0012. 2'7, 1961FIGZ INVENTOR.

ATTORNEY.

RONALD E. WALKER.

United States Patent 3,136,221 RECIPROCATORY TELESCOPING-PISTONHYDRAULIC MUTOR Ronald E. Walker, Riverside, Ontario, Canada, assignorto Phil Wood industries, Windsor, Ontario, Canada, a corporation ofCanada Filed Oct. 27, 1961, Ser. No. 148,222 7 Claims. (11. 91-168) Thisinvention relates to reciprocatory hydraulic motors and, in particular,to telescoping-piston reciprocatory hydraulic motors.

One object of this invention is to provide a reciprocatorytelescoping-piston hydraulic motor equipped with cushioning means forretarding the speed of travel of the telescoping pistons by releasinghydraulic pressure fluid as they approach either or both ends of theirstrokes, thereby preventing the shocks which hitherto have occurred bythe pistons engaging in metal-to-metal contact at the ends of theirstrokes.

Another object is to provide a cushioned-stroke telescoping pistonreciprocatory hydraulic motor, as set forth in the preceding objectwherein the retardation of the speed of travel of the pistons is broughtabout by providing auxiliary discharge ports opened to the exhaustcircuit as the pistons near the ends of their working strokes.

Another object is to provide a cushioned-stroke telescoping-pistonreciprocatory hydraulic motor, as set forth in the preceding objectswherein the auxiliary discharge ports are opened as a result of beinguncovered by their associated telescoping pistons or, in the case of theoutermost piston, in co-operation with one or more ports in the cylinderwall, so as to release fluid and relieve the hydraulic fluid pressurenear the end of the stroke of each piston, as a result of the travel ofeach piston itself.

Another object is to provide a double-acting reciprocatorytelescoping-piston hydraulic motor, as set forth in the precedingobjects, wherein cushioning is effected on both the forward andretraction strokes.

Other objects and advantages of the invention will become apparentduring the course of the following description of the accompanyingdrawings, wherein:

FIGURE 1 shows a cushioned-stroke telescoping-piston reciprocatoryhydraulic motor, according to one form of the invention, with the upperhalf of the figure in central vertical section and the lower half mainlyin side elevation with the pistons at the ends of their rearward orretraction strokes; and

FIGURE 2 is a fragmentary central vertical longitudi nal section showingthe innermost telescoping piston and the next adjacent piston in theirrelative positions at the ends of their working or forward strokes.

Referring to the drawing in detail, FiGURE 1 shows a cushioned-stroketelescoping-piston reciprocatory hydraulic motor, generally designated10, according to one form of the invention as consisting generally of anelongated hydraulic cylinder 12 within which is mounted a first hollowpiston 14. Reciprocably mounted within the first piston 14 is a secondhollow piston 16, Within which is reciprocably mounted a third hollowpiston 18, within which is reciprocably mounted a fourth hollow piston20. The fourth or innermost piston 20 also serves as a hydraulicpressure fluid supply conduit in one direction of operation and as afluid discharge conduit in the op posite direction'of operation and isalso connected to the load to be moved, such as to the dump body of adump truck (not shown), as explained more fully below.

The hydraulic cylinder 12 has an elongated tubular cylinder barrel 22 tothe rearward end of which is secured a cylinder head 24 to which in turnis secured a rearwardly-projecting bracket structure 26 carrying abearing boss 28 in which is mounted asleeve bearing 30 containing abearing bore 32. The bearing 30 and the bearing boss 28 are drilled toreceive a lubricant fitting 34 by which the lubricant is supplied to thebearing bore 32. The latter receives a pivot shaft (not shown) mountedin any conventional manner upon a truck or other vehicle chassis (notshown) by which it can swing upward or downward while performing itswork, as explained below in connec-' tion with the operation of theinvention.

The cylinder barrel 22 contains a cylinder bore 36, the rearward end ofwhich is internally threaded to receive the correspondingly-threadedreduced diameter portion The inner end of each annular closure head 40,42, 44

or 46 is bored as at 48 and counterbored as at 50 to re-' ceive aconventional packing 52. Each counterbore 50 at its outer end isinternally threaded to receive an annular packing-compressing ring orgland 54 in the form of an annular internal nut. The cylinder barrel 22near the head 24 has axially or longitudinally-spaced ports 56 and 58which register with correspondingly-spaced ports 60 and 62 in anelongated boss 64 welded or otherwise secured to the cylinder barrel 22near the cylinder head 24 thereof (FIGURE 1). Bolted as at 66 to theboss64 is a hollow service casing 68 having a rearward service port 70registering with the rearward ports 56 and 60 and opening into a chamber72 from which the service port 74 opens outward and is connected in anysuitable way to a hydraulic fluid conduit (not shown).

Registering with the port 62 in the boss 64 is a threaded port '76 intowhich is threaded a tubular check valve casing 7'8 located in thechamber 72 and having a valve seat port registering with the ports 62and 58. Mounted within the valve casing-78 is a check valve mem-' ber orball 82 which isurged into engagement with the valve seat port 80 by acompression spring 84, the opposite or upper end of which engages theinner surface of the casing 68 as an abutment. A gasket .86 isinterposed between the boss 64 and the casing 68'to prevent leakage, andis drilled or punched in alignment with the ports 60 and 62 to permitpassage of fluid therethrough. The first, second and third tubularpistons 14, 16 and 18 are provided with enlarged piston heads 88, and 92respectively which have central ports 94, 96 and 9,8 therethrough. Thefirst, second and third piston heads 88, 90 and 92 adjacent theirrespective tubular piston rods 89, 91 and 93 are annularly grooved forthe reception of the usual piston rings 100 for, preventing leakage. Inthe first, second and third tubular piston rods 89, 91 and 92 and inclose proximity to the first, second and third piston heads 88, 90 and92 are ports 102, 104 and 106. The fourth piston 20 is of slightlydifferent construction in that its piston head 108 is composed ofseveral pieces, the principal piece being a head member 110 having anexternally-threaded reduced diameter portion 112 upon which is threadedan internally-threaded ring 114 of.

slightly greater diameter than the head member 110 so as to serve as astop providing an annular. shoulder 115 extending above the cylindricalside surface 116.

The side surface 116 terminates at an annular shoulder 118 on anenlarged diameter portion 120, the head member 110 at this locationhaving an internally-threaded socket 122 into which is threaded theinner end of a tubular piston rod 124. The piston rod 124 and enlargedportion are drilled to provide a port 126 containing a tubular roll pin127 with a gap or slot along one. side thereof opening into a passageway128 through the center of the hollow piston rod 124. Slidably mountedupon the side surface 116 of the head member 110 for axial orlongitudinal travel between the annular shoulders 115 and in 118 is asliding valve sleeve 130 which is circumferentially-grooved to receivepiston rings 132 which in turn engage the inner wall of the adjacentthird piston 18 for preventing leakage therebetween. The inner wall ofthe outer end of the third piston 18, adjacent its annular closure head46, is provided with four circumferentiallyspaced elongated axialgrooves 134 (FIGURE 2) which bypass the sliding valve sleeve 139 so asto enable flow of hydraulic fluid past the latter when the hydraulicmotor is in its fully-extended position ready to start its retractionstroke.

Near its outer end, outside the annular closure head 46 of the thirdpiston 18, the fourth piston is providedwith a port 36 leading into thepassageway 12; and having an internally-threaded coupling sleeve orbushing 138 welded or otherwise secured to'the fourth piston 20 so as toprovide means for coupling a flexible hose to the fourth piston 20. Theextreme outer end of the fourth piston 20 is provided with a cylindricalrecess 1411 within which is secure, as by welding, a bearing bushing 142having a bearing bore 144 to which lubricant is supplied through alubricant fitting 1415.

In the operation of the invention, let it be assumed that the serviceports 74 and 136 are connected by flexible high pressure hoses to aconventional four-way hydraulicv control valve and thence to a hydraulicpump or other suitable source of hydraulic pressure fluid (not shown)which in turn is connected to a hydraulic fluid reservoir (not shown).-Let it also be assumed that the telescoping hydraulic motor 10 is in itsretracted position (FIGURE 1), such as when the dump body of a dumptruck is in its lowered or horizontal position and that it is desired toextend the motor 19 upon a working stroke to lift'one end of the dumpbody or perform other useful work by moving a particular load (notshown).

To cause the first, second, third and fourth pistons 14, 16, 18 and 20to move outward to the right from their retracted positions shown inFIGURE 1, the control valve is so shifted'as to connect the service.port 74 to the pump or other source of hydraulic pressure fluid .andthe service port 136 to the hydraulic fluid reservoir connected to thesuction side of the pump.

Under these conditions, hydraulic pressure fluid flows from the serviceport 74 through the chamber 72, ports 78, 6t) and 56 into the endchamber of the hydraulic cylinder 12 adjacent the cylinder head 24,acting against the piston head 88 of the first piston 14 to move itoutward to the right and closing the port 58 in passing. Atthe sametime, pressure fluid flows from the end chamber of the hydrauliccylinder 12 of the cylinder bore 36 through the centralpiston head ports94, 96 and 98, acting against the piston heads 9! 92 and 108 to move thesecond, third and fourth pistons 16, 18 and 20 outward to the right andclosing the ports 102, 164 and 106 in passing. During this part of thecycle of operation, pressure of the pressure fluid within the valvechamber 72 acts against the ball check valve 82 to force it into closingengagement with its valve seat port 80 so as to temporarily prevent flowof fluid from the chamber 72 into the port 62. The ball check valve 32remains closed by the pressure of the pressure fluid in the chamber 72,aided by the spring 84 even after the piston head 88 completely passesthe cylinder wall port 58.

Meanwhile, pressure fluid flowing past the ring 114 of the fourth pistonhead 1118 acts against the left-hand end of the sliding valve sleeve 130and forces it into the position shown in FIGURE 1 against the annularshoulder 118 as the fourth piston 20 moves outward to the right. At thesame time, fluid displaced from the cylinder space within the cylinderbore 36 to the right of the piston head 83 and from the spaces withinthe first, second, third and fourth pistons 14, 16, 18 and 24) to theright of their respective piston heads .88, 9t

- 92 and 1% escapes through their respective ports 162,

' hydraulic fluid tank.

motor wherein 194, 1dr? and 126, thence through the tubular roll pin127, the passageway 12% and the port 136 back to the hydraulic fluidreservoir. In this manner, the first, sec- 0nd, third and fourth pistons14, 16, 1S and 21) are moved outward to their extended positions, movingthe load to which the fourth piston 20 is connected at the bearingbushing 142, for example, tilting the dump body to discharge its load.

When the first, second and third pistons 14, 16 and 18 have reachedtheir fully-extended positions in this manner, and the fourth piston 29is nearing its fully-extended positiomthe sleeve 13% adjacent the headmember 11!) thereof passes beneath the longitudinal groove 134,permitting pressure fluid to escape around the valve sleeve 13! throughthe port 126, the slotted tubular roll pin 127, passageway 128 andservice port 136 back to the This action retards the speed of andcushions the telescoping pistons 14, 16, 18 and 20 as they near the endsof their forward or working strokes.

Tooperate the motor 11 so as to retract the telescoping pistons 14, 16,18 and 21 the operator reverses the four-way control valve (not shown)so as to supply hydraulic pressure fluid to the service port 135 andexhaust hydraulic fluid from the service port 74. Hydraulic pressurefluid then flows via the service port 135 through the passageway 128,the slotted tubular roll pin 1 27 and port 126, shifts the valve sleeveto the left (FIGURE 2), and flows through the groove 134 and ports'126,1535, 104 and 1192 into the annular chambers between the respectivetubular piston rods, and acts against the innermost piston head member119 and against the respective annular piston areas behind the pistonheads 92, 9t and 99 to cause the pistons 20, 18, 16 and 14 to moveinward to the left upon their rearward or retraction strokes,telescoping with one another as they do so. When the first piston head38 nears the end of its retraction stroke and uncovers the port 58 inthe cylinder barrel 22, the pressure fluid thenceforth passes throughthe ports 53, 62 and 86, lifting the ball check valve 32, and escapesthrough the valve casing chamber 72 and service port 74 back to thehydraulic fluid tank. This action cushions the retraction strokes of thetelescoping pistons 2d, 18, 16 and 14 as they reach the limits of theirreturn or rearward strokes by retarding their speeds. Meanwhile, thehydraulic fluid displaced from the spaces to the left of the respectivepiston heads 88, 91?, 92 and 1tl8'escapes through the ports 38, '96, 94and 56, tit? and 711 into the valve casing chamber 72, and thencethrough the service port 74 back to the hydraulic fluid tank.

In the manner just described, the present invention provides atelescoping-piston reciprocatory hydraulic the strokes of thetelescoping pistons are cushioned by theprovision for the automaticrelease of pressure fluid at the opposite end of their strokes, achievmgthe objects set forth above at the beginning of the presentspecification.

What I claim is:

1. reciprocatory telescoping-piston hydraulic motor comprising acylinder, a plurality of hollow hydraulic pistons ofsuccessively-decreasing diameters mounted within said cylinder incoaxial telescoping relationship for extension during their forwardstrokes and retractron during their return strokes, the outermost pistonhaving a tubular piston rod and a piston head thereon reciprocablymounted in said cylinder and the remaining pistons having tubular pistonrods and piston heads thereon reciprocably mounted in the tubular pistonrods of the next larger diameter piston, means for supplyinghydraulicpressure fluid to said cylinder and pistons on one side of said pistonheads and exhausting pressure fluid from the opposite side thereof, andmeans including cooperating elements disposed adjacent one another onsaid innermost piston and piston immediately adjacent thereto forreleasing hydraulic pressure fluid and effecting retardation of saidpistons in response to the arrival of said pistons at predeterminedfluidreleasing locations near the ends of their forward strokes.

2. A reciprocatory telescoping-piston hydraulic motor, according toclaim 1, wherein said hydraulic pressure fluid releasing means alsoincludes ports in piston rods adapted to be uncovered by the adjacentpiston heads and placed in communication with one of said cooperatingelements at said fluid-releasing locations.

3. A reciprocatory telescoping-piston hydraulic motor, according toclaim 1, wherein said hydraulic pressure fluid releasing means includesan axially-elongated passageway in one of said piston rods disposed influidbypassing relationship with the piston head of the next adjacentpiston engageable therewith. Y

4. A reciprocatory telescoping-piston hydraulic moto according to claim3, wherein said next adjacent piston head includes a valve memberaxially slidably mounted thereon.

5. A reciprocatory telescoping-piston hydraulic motor,

according to claim 4, wherein the piston head of said innermost pistonhas a portion fixedly attached to the innermost piston rod and whereinsaid axially-slidable valve member includes a hollow cylindrical pistonhead portion slidably mounted on said fixedly attached portion insealing engagement with said cylinder.

6. A reciprocatory telescoping-piston hydraulic motor, according toclaim 5, wherein said next adjacent piston rod has an axially-elongatedfluid bypass passageway disposed in bypassing relationship with saidhollow cylindrical piston head portion near one end of the stroke ofsaid innermost piston.

7. A reciprocatory telescoping-piston hydraulic motor, according toclaim 3, wherein said passageway comprises a groove in the inner wall ofsaid next-adjacent piston rod and exceeding the axial length of saidvalve member.

References Cited in the file of this patent UNITED STATES PATENTS2,364,741 Merchant Dec. 12, 1944 2,438,285 Houldsworth Mar. 23, 19482,517,153 Wood Aug. 1, 1950 2,783,744 Tennis Mar. 5, 1957

1. A RECIPROCATORY TELESCOPING-PISTON HYDRAULIC MOTOR COMPRISING ACYLINDER, A PLURALITY OF HOLLOW HYDRAULIC PISTON OFSUCCESSIVELY-DECREASING DIAMETERS MOUNTED WITHIN SAID CYLINDER INCOAXIAL TELESCOPING RELATIONSHIP FOR EXTENSION DURING THEIR FORWARDSTROKES AND RETRACTION DURING THEIR RETURN STROKES, THE OUTERMOST PISTONHAVING A TUBULAR PISTON ROD AND A PISTON HEAD THEREON RECIPROCABLYMOUNTED IN SAID CYLINDER AND THE REMAINING PISTONS HAVING TUBULAR PISTONRODS AND PISTON HEADS THEREON RECIPROCABLY MOUNTED IN THE TUBULAR PISTONRODS OF THE NEXT LARGER DIAMETER PISTON, MEANS FOR SUPPLYING HYDRAULICPRESSURE FLUID TO SAID CYLINDER AND PISTONS ON ONE SIDE OF SAID PISTONHEADS AND EXHAUSTING PRESSURE FLUID FROM THE OPPOSITE SIDE THEREOF, ANDMEANS INCLUDING COOPERATING ELEMENTS DISPOSED ADJACENT ONE ANOTHER ONSAID INNERMOST PISTON AND PISTON IMMEDIATELY ADJACENT THERETO FORRELEASING HYDRAULIC PRESSURE FLUID AND EFFECTING RETARDATION OF SAIDPISTONS IN RESPONSE TO THE ARRIVAL OF SAID PISTONS AT PREDETERMINEDFLUIDRELEASING LOCATIONS NEAR THE ENDS OF THEIR FORWARD STROKES.